The items that are stored in mobile phones during their use, such as entries in the phonebook, sent and received messages, call records, photos, sound recordings, documents etc., are becoming more and more personal and some of the information in these items can be considered as private or sensitive by the user of the mobile phone. Teenagers may have “secret” friends and business people may have “secret” contacts, etc.
Thus, users may not wish that all the information in their mobile phones is easily accessible to others (unauthorized users). The same problem also exists for personal computers, but in contrast to personal computers it is not uncommon to borrow out one's mobile phone to allow somebody to make a call while it is unlikely that users borrow their personal computers for somebody to send an e-mail. While the mobile phone is borrowed, the borrowing person can access some of the sensitive or private information in a matter of seconds in conventional mobile phones.
Protection of sensitive or private information is known in the form of password protected data. However, it is well-known that end-users are not fond of using passwords and therefore protecting for example certain contacts (the entries) in the phonebook of a mobile phone via passwords is not a viable option.